1. Field of the Invention
The present invention relates to a control device mounted on a vehicle, and more particularly to a control device for controlling power generation of a power generator mounted on a vehicle such as a car and a truck.
2. Description of the Related Art
Conventionally, a control device used for controlling power generation based on rotation speed of the on-vehicle power generator has been known.
Particularly, the control device of the on-vehicle power generator detects rotation speed based on alternating current voltage appearing in a stator winding. When the detected rotation speed exceeds a reference rotation speed, the control device allows the on-vehicle power generator to start power generation. When the detected rotation speed becomes lower than the reference rotation speed, the on-vehicle power generator stops power generation. When the reference rotation speed is set to a value that is too small, erroneous detection may occur in response to noise and the like. Therefore, the reference rotation speed is preferably set to a value that is large to a certain extent. During low-temperature startup in winter, in particular, when ambient temperature is low, operation is started at a higher rotation than in other seasons. Therefore, the reference rotation speed can be set to a high value. However, when the reference rotation speed is set to a value higher than the idling rotation speed after the end of a warm-up operation of the engine, an issue occurs in that power generation cannot be continued during idling, such as when waiting for a traffic signal to change.
To avoid such issues, for example, Japanese Patent No. 4006941 discloses an on-vehicle power generation control device that performs control to start power generation when a phase voltage of a stator winding exceeds a first reference frequency, and to stop power generation when the phase voltage becomes lower than a second frequency that is lower than the first reference frequency.
During low-temperature startup, even when the rotation pulse of the engine due to ignition is large and the actual rotation speed (average rotation speed) is low, the on-vehicle power generation control device disclosed in Japanese Patent No. 4006941 may start power generation when a high rotation portion of the pulse becomes higher than the first reference frequency. Once power generation is started, power generation torque is applied regardless of the actual engine rotation being low. Therefore, although engine rotation once again drops below the rotation speed equivalent to the first reference frequency before sufficiently increasing, power generation torque is sustained because power generation is not stopped. As a result, engine startup is delayed. A problem occurs in that startability deteriorates. The deterioration in startability also causes engine stalling. Therefore, improvement is desired.